Means for improving combustion of fuel



Dec. 13, 1% 1. A. DOW, JR, ETAL 3 9 MEANS FOR XMPROVING COMBUSTION OF FUEL Filed Feb. 23, 1965 United States Patent 3,291,182 MEANS FQR HML RUVKNG CUMEBUSTKUN 9F FUEL Irving A. Bow, Jr. and Martin Aarflot, Elizabeth, N..l.; said Aiarfiot assignor to said Dow Filed lFehO 23, M65, Ser. No. 434,261 3 Claims. (\Cl. 158-15) The present invention comprises a novel means for delivering secondary air to oil burner furnaces. When there is incomplete combustion of fuel in a furnace, fuel is wasted and ungasified products of the incomplete combustion, such a soot, deposit in the boiler tubes reducing the heat conductivity of the tubes, and also are carried out the chimney to pollute the surrounding atmosphere. In the usual oil burner furnace, secondary air is supplied for the purpose of obtaning comzlete fuel combustion. However, the results so far obtained have not materially reduced soot deposition or improved furnace efliciency. We have found that when secondary air is preheated and delivered under pressure in jets directed at the side of the flame from the burner, the resulting turbulence of the flame created by the air jets, together with the additional air provided by the air jets, results in complete combustion of fuel within the furnace chamber. Furnaces operated by us with this type of secondary air are surprisingly efficient, as compared to furnaces relying upon natural draft for induction of secondary air or which are provided with means for delivering secondary air under pressure in an annulus about the flame. No soot deposited on the burner or on the furnace walls and no pollution of the atmosphere resulted. The saving in fuel was surprisingly great.

Preheating of the secondary air and formation of the jets directed to the burner flame is obtain d, in accordance with the invention, by placing a heat exchanger and turbulator of novel construction within the furnace to one side of the flame and coupling the inlet thereof to the outlet of a blower adapted to supply the des red volume of air. The device comprises inner andouter coaxial cylindrical members defining an annu ar space therebetween, one end of the inner member being coupled to the blower for reception of air under pressure therefrom and the outer member being closed at its ends and having a longitudinal row of apertures through its cylindrical wall for emission of air in jets from the annular space. The other end of the inner member has apertures in its cylindrical wall through which air passes into the annular space between the members. A spiral fin or web extends from one end of the annular space to the other end and this web causes the air to flow in a spiral path through the annular space. The spiral web thu insures circulation of the air in its passage to the apertures in the outer member and also serves to conduct heat from the outer to the inner member, tending to equalize the temperatures of the members.

For a better understanding of the invention and of a specific construction of the apparatus, reference may be had to the accompanying drawing of which the single figure is a diagrammatical view of a boiler furnace equipped with the econdary air control means of the invention.

In the drawing, a heating plant 2 is diagrammatically shown as comprising two sets of fire tubes 4 and 5 within a boiler vessel 6, a conventional cone burner 7, with its fuel and primary air supplies (not shown), furnace floor 8, furnace front wall it supporting the cone burner, rear furnace wall 11 and bridge wall 12 above which the combustion gases pass to the tubes 4. In accordance with the invention, a cylindrical member 13 is mounted in wall to in any suitable manner to extend into the furnace chamber parallel to the floor 8. Induced draft furnaces ordinarily have an opening in the wall thereof, such as that indicated at 14 in the drawing. Such an opening, if present, affords a convenient mounting location for member 13. Mounting plates 16 and 18 are secured to the inner and outer surfaces of Wall It) to seal off the opening 14. The plates are provided with aligned circular openings for reception of member 13. Member 13 extends slightly outside the furnace and is connected through a hose 25 to a power driven fan 22 for reception of secondary air under pressure therefrom. Preferably, an adjustable control valve 23 is provided at the fan outlet. The other end of member 13 is closed except for an outlet 24 therein for ejection of air into the furnace at an angle to the bridge wall 12. Surrounding member 113 is a cylindrical shell 28 which is sealed at its ends to member 15. In the annular space between the walls of member 13 and shell 28 i a spiral web or fin 30 which extends for the full length of the shell. Four or more openings 32 in member 13 near the inner end thereof permit air to enter the annular space between the member and shell. The shell is provided with a plurality of orifices 34 opening into the furnace chamber and through which air is ejected from the annular space in jets indicated diagrammatically at 36.

in operation, air from the blower 22 enters the inner member 313 and flows through the length thereof. During passage through member 13, the temperature of the air is increased moderately due to the temperature of the furnace and due to the conduction of heat from the shell to the wall of member 13 by the spiral Web 30. When the air enters the annular space through orifices 32, its temperature is increased considerably because of the hot walls of the shell. Some of the air entering the annular space exits through the first opening 34, the remainder of the air passing along the spiral web with increased velocity. As each orifice 34 i approached, some of the air leaves the annular space and emerges as a jet 36. The spiral web 3t) insures that the hotter air flowing in the annular space will circulate about the surface of the inner Inemberltii within which the cooler air flows in the opposite direction, thus providing optimum heat exchange and distribution. The web 30 also avoids formation of pockets of stagnant air in the annular space that would act as heat insulators. The jet of air 38 issuing from orifice 24 tends to move the tip end of the flame upwardly and toward the passage 3h above bridge wall 12. The jets 2-6 and 38, as heretofore described, create turbulence in the flame and atomize the particles therein to insure complete combustion.

The above described device has been found to yield in practice substantial savings and to result in clean furnace walls and clean burners with no deposition of soot thereon or in the boiler tubes. As an example, numerical values of one installation in accordance with the invention will be given. It will be understood that the dimensions of the heat exchanger and turbulator and the horsepower of the blower will vary with the particular furnace or with the size of the burner and that additional units could be provided for large installations. Also, the location of the heat exchanger and turbulator will depend upon the location of the burner in the furnace, it being necessary only that the device he so located with reference to the burner that the jets of preheated secondary air issuing from the device will not be directed substantially in the direction of the flame from the burner and preferably substantially perpendicular thereto. For example, the device could be mounted in the wall above the burner rather than below or, where the burner is mounted to produce a vertical flame, the heat exchanger would be mounted vertically so that the jets of air therefrom would strike the flame substantially perpendicular to its direction of flow. Alternatively, the device could be mounted in a wall opposite to that in which the burner is mounted, in which case the orifices in shell 28 would be so located as to direct jets toward the burner. The specific example is as follows:

Diameter of member 13 6 inches.

Length of member 13 37 inches.

Diameter of 8 orifices 32 2 inches.

Diameter of shell 28 10 inches.

Length of shell 28 24 inches.

Number of holes 34 10.

Diameter of holes 34 1% inches.

Burner capacity 25-40 gallons per hour.

Fan outlet 3 inches by 4 inches.

Horsepower of fan 0.08 capable of delivering 328 cubic feet per minute against static pressure of 0.2 inches water.

The above specific figures are for a one-burner furnace. For larger furnaces, more powerful fans and larger turbulat-ors would be employed or additional devices could be used. For proper correlation of the particular blower to the dimensions of the turbulator, the resistance to the air offered by the device is determined and from such resistance the capacity of a suitable fan may be readily determined. Although in the specific example the shell 28 was provided with ten orifices 34, obviously a single long slot in the shell emitting a sheet-like jet could serve the same purpose or, in the case of small furnaces, a single orifice could be employed.

From the foregoing description, it will be apparent that the invention provides a novel apparatus and method for insuring complete combustion in an oil burner furnace. Although the furnace illustrated in the drawing happens to be of the type in which the flue gases pass through the boiler tubes, obviously the invention is equally applicable to furnaces in which the water is circulated in the boiler tubes. The invention is applicable to furnaces of a wide range of capacity. Furnaces for supplying heat to apartment houses, oflice buildings, and the like could advantageously employ the invention, not only for fuel conservation, but also to avoid pollution of the atmosphere. The invention could also be employed in relatively small installations as, for example, in furnaces for heating individual homes.

The following is claimed:

1. The combination with a fuel burner furnace of a secondary air supply means comprising a source of air under pressure, a device within the furnace spaced laterally from the burner and having inner and outer cylindrical members defining a closed ended annular space therebetween, means coupling one end of said inner member to said source for reception of air under pressure therefrom, said inner member having openings therethrough adjacent its other end for passage of air into said annular space and said outer member having at least one orifice in its wall for emission of a jet of air therethrough, and means within said annular space for causing air therein to circulate about the inner member.

2. The combination according to claim 1 wherein said means for causing air circulation about the inner member is a spiral web that serves also for heat conduction between said members.

3. The combination according to claim 1 wherei said outer member has a plurality of apertures therein for emission of jets of air therethrough and wherein said inner member at the end remote from said source has an aperture therein for directing a jet of air into the furnace at an angle to the jets delivered through said apertures in the wall of the outer member whereby, when the burner emits a horizontal flame and said exchanger is positioned therebeneath, the vertical jets from the outer.

member impinge on the flame at the lower side thereof and the jet from said aperture in the end of the inner member is directed at the tip of the flame to raise the same and augment the turbulation effected by said vertical jets.

References Cited by the Examiner UNITED STATES PATENTS 805,671 11/1905 SaflFell 158-1 1,605,403 11/ 1926 Heckeroth 1581 FOREIGN PATENTS 702,428 1/1965 Canada.

FREDERICK L. MATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner. 

1. THE COMBINATION WITH A FUEL BURNER FURNACE OF A SECONDARY AIR SUPPLY MEANS COMPRISING A SOURCE OF AIR UNDER PRESSURE, A DEVICE WITHIN THE FURNACE SPACED LATERALLY FROM THE BURNER AND HAVING INNER AND OUTER CYLINDRICAL MEMBERS DEFINING A CLOSED ENDED ANNULAR SPACE THEREBETWEEN, MEANS COUPLING ONE END OF SAID INNER MEMBER TO SAID SOURCE FOR RECEPTION OF AIR UNDER PRESSURE THEREFROM, SAID INNER MEMBER HAVING OPENINGS THERETHROUGH ADJACENT ITS OTHER END FOR PASSAGE OF AIR INTO SAID ANNULAR SPACE AND SAID OUTER MEMBER HAVING AT LEAST ONE ORIFICE IN ITS WALL FOR EMISSION OF A JET OF AIR THERETHROUGH, AND MEANS WITHIN SAID ANNULAR SPACE FOR CAUSING AIR THEREIN CIRCULATE ABOUT THE INNER MEMBER. 